Production wells penetrate subterranean formations whose yield, besides the desired lighter fluid, such as oil, includes a heavier undesirable fluid, such as water. Over time the percentage of water produced from the formation typically increases. The production of water to the ground surface results in increased costs in both the energy to lift the water to the surface and in surface handling. Accordingly, many wells become uneconomic due to excess water production.
The traditional method for producing a well with a high water-cut is to produce the total reservoir fluid to the surface. At the surface the water is separated from the desired hydrocarbon portion of the reservoir fluid. Disposal of the water is then commonly achieved by transportation to a disposal well where it is injected into an injection formation or zone. Thus, production of excess water to the surface significantly increases the costs of well operations and the risk of environmental impacts.
A second method of addressing high water-cut reservoir fluid is referred to as an “in-situ” approach. In the in-situ approach, the undesired water and the desired hydrocarbons are allowed to substantially separate in the wellbore. The desired fluid portion, and typically a portion of the undesired fluid, is then produced to the surface and the undesired portion is injected into a disposal formation (“injection zone”). The injection zone may be located above or below the producing reservoir formation.
While the prior in-situ systems provide the opportunity to decrease operation costs and thus increase a well's economic life, drawbacks have been noted in terms of compensation in changes in the water-cut of the reservoir fluids, compensation for changes in injectivity of the injection zone, complexity, and reliability. Thus, there is still a need for a downhole production and injection pump system that addresses increasing need to economically produce desired reservoir fluids to the surface from high water-cut reservoirs.